1. Field of the Invention
This invention relates to the construction industry, and more specifically to a scaffolding brace that is attached to and supported by the upright studs used in both commercial and residential construction. The scaffolding brace of this invention is designed to be quickly secured to two adjacent parallel wall studs which may or may not have been previously covered with a facing/sheathing material and insulation. The scaffolding brace may be used individually to provide a small platform upon which an individual may work, or multiple scaffolding braces can be used to provide support for planking suspended between pairs of the scaffolding braces.
2. Description of Prior Art
Typically, during frame building construction, after the basic frame is erected and exterior sheathing has been applied, carpenters and roofers need to work high up on the exterior of the building to begin roof installation or to finish work on the cornice. Presently in residential construction, three methods are used to provide scaffolding upon which workmen may stand when working on the exterior of a building. The method most frequently used by far is to build wooden scaffolding which is directly attached to the structure. To build these scaffolds, at the corners of the building horizontal supports which extend beyond the face of the building are first nailed through the exterior sheathing into the studs. Supporting braces attached to the end of the horizontal supports and the side of the building are placed at approximately 45 degrees to form triangular supports. The provision of horizontal supports along a face of the building is more difficult. Holes, sufficiently large to pass horizontal supports are first cut through the exterior sheathing. The horizontal supports, which are typically two by fours, are then passed through these holes and nailed to studs within the building. Frequently, no interior studs are positioned in the correct location and additional framing is required within the building to firmly anchor the horizontal supports. To complete the scaffolding, long planks are then laid between the extended horizontal supports. For each face of the building where scaffolding is required, this process is repeated. There are several problems with this method of scaffold construction. First, limited load bearing and very little lateral stability is provided by the extended horizontal supports and the erected scaffolding can be dangerously unstable. Frequently the horizontal supports break under the cantilever loads where knots weaken the wood. Further, not only does this method leave holes in the exterior sheathing which then need to be repaired, but the presence of the horizontal members and associated framing within the building makes interior work more difficult. Additionally, the effort required to assemble and disassemble the scaffolding adds significant extra time which skilled carpenters need to spend on the job. Finally, lumber costs and use increase with the extent of the scaffolding required.
Two alternative methods are currently employed to cut down on the time, labor, and material required to build attached wooden scaffolding. The first of these alternative methods makes use of the ladders always present at a construction site. Two or more ladders (depending on the length of the building) are extended and placed against the face of the building well above the height at which the scaffolding is desired. A horizontal support bracket (ladder jack) is attached to two or more rungs of each of the ladders. Planking is then carried up by two men, one on each ladder, and laid on the jacks between the ladders. There are also several problems with this scaffolding method. First, it is difficult to firmly set the feet of the ladders on the uneven, recently excavated, and frequently muddy soil surrounding a building site. Even when a firm footing is secured, an additional difficulty is encountered because the footings must be of the same relative height to the building (or off by a full ladder step spacing) so that the ladder jacks are at the same height in order to make the scaffold planking relatively level. Again, relatively little lateral stability is achieved by extending a single supporting ladder jack from each ladder. The ladders themselves also set a limit to the weight which can be placed upon the scaffolding. Generally, each ladder may only be rated to hold 250 pounds on each step. Thus, for two adjacent ladders, the weight of the ladder jacks, the planking, the construction supplies to be used, and the workmen many not safely exceed 500 pounds. Use of the planking by two fully grown carpenters quickly approaches the safety limits which are, in fact, often exceeded. Finally, the ladders themselves get in the way of workmen walking along the scaffold.
The second alternative scaffolding method is not much better. Instead of ladders providing the vertical support, wooden (or aluminum) columns are used to support pump jacks. Typically, standard two by fours available at the construction site are overlapped and nailed together to form a long column with an approximately square cross section. The length of the column is slightly greater than the ground to roof height of the building. At what will be the top end of the column, metal straps are attached to the column while the bottom end of the column is placed through a pump jack. The pump jack has a mechanism for gripping and advancing the jack up the wooden column and an extension upon which planking may be placed. The wooden column is erected near the face of the building and fastened at its top end with the straps to the roof. Two or more such wooden columns are erected and their bases secured. In use, planks are laid across the horizontal extensions of the jacks on adjacent columns to form a scaffold upon which the "pumpers" can stand. The jacks are then "pumped" up the columns by workmen operating pump levers on the side of each jack. As can be readily appreciated, this scaffolding system suffers most of the same problems of lateral stability and anchor stability as the ladder jack system. It also adds the complexity that during the pumping operation, two or more workmen must carefully coordinate their efforts to maintain the planking relatively level. Given the drawbacks of the ladder jack and pump jack systems, it is no wonder that the time and material intensive system of building attached wooden scaffolding is preferred.
For interiors use, such as when exceptionally high walls or vaulted ceilings are constructed, attached wooden scaffolding is almost always used since the ladder jack system is too difficult to manage in limited interior spaces. As with external use, the lateral stability of the wooden scaffold is a problem although the scaffold may be tied to additional studs to reduce the problem. However, interior wooden scaffolding does limit the amount of additional interior work which can be done until the scaffolding is removed.
The prior patent art of scaffold brackets and support for roofers, painters, and carpenters has a long history. Ramsey, in U.S. Pat. No. 474,406, in 1892, disclosed a window jack for supporting scaffolding along the side of a building under construction. Ramsey's window jack was a triangular brace which was designed to engage the frame of a window from the inside and extend outside where scaffold planking could then be placed on the jack. Once locked onto the window frame, the bracket was stationary. In order to support two ends of the scaffolding, two such window jacks would have to be used locking against adjacent windows or door frames in the structure. Provision was made for adjustment, in a preferred embodiment, to windows of different widths.
In U.S. Pat. No. 945,162, Hause describes a variation of a window jack which was designed to go through a window opening and be secured to the inside window frame, in which the triangular brace for the jack was fastened by links which locked the triangular form into place when the jack was opened or closed. The improvement of this invention was that the links lock the jack open in its open position and lock the jack closed in its closed position so that, when carried, the jack did not unexpectedly open and injure the carrier.
More recently, Shoemaker in U.S. Pat. No. 3,698,680 described a scaffold-support bracket which could be easily attached to a wall form erected to contain poured concrete. Like Ramsey and Hauge, Shoemaker's support bracket consisted of a single triangular bracket with an extension which hooked behind a stationary support. In Shoemaker's case, the stationary support was not a window frame but rather one of the upright posts (strongbacks) erected to take the weight of the poured concrete. Bondi, in U.S. Pat. No. 3,804,199, takes another approach to fastening a triangular support bracket by securing the bracket with a bolt, which passes through the bracket and the vertical support, and is typically used with masonry as in Mausoleum construction. Bondi's bracket may be mounted flush to the face of the masonry as long as access to the other side of the masonry is possible to secure the bolt.
Another approach is illustrated by Sickler in U.S. Pat. No. 4,452,336. Sickler describes a stud gripper which is designed to securely embrace the two sides of a wall stud and provide further support for a two by four. Two stud grippers on studs on one side of a room supporting a two by four between them can be matched with a similar set of grippers on the other side of a room to provide parallel horizontal two by fours upon which scaffold planking can be erected. Nails or bolts may also be used to secure the stud grippers to the studs. A triangular bracket may also be secured to the stud grippers to directly provide support for planking.
Gregory, in U.S. Pat. No. 4,673,060 takes a more direct approach to securing a foldable triangular bracket to an upright by using bolts to attach both the horizontal member and the support member to the stud. Holes are positioned vertically along the stud which is typically a part of a gangform for pouring concrete walls. Scaffold planking is then suspended between two or more attached triangular brackets.
An alternative to supporting the bracket directly from the studs is present by Lapp in U.S. Pat. No. 5,503,358. Lapp hangs a vertical member by a bracket from the top of an erected wall and secures a foldable triangular bracket to the vertical member. For walls of varying thickness, the width of the hanging bracket is adjustable. Essentially, Lapp's triangular bracket attaches to the vertical hanging member much as Gregory's bracket attached to his stud. Recently, Savitski in U.S. Pat. No. 5,535,974 describes a variation of the early triangular brackets which were somehow fixed to the backside, or inside, of a support (such as a window). In Savitski's device, a gripper arm having two grippers which engage the front and back of a stud is rigidly attached to a horizontal member and a support member to form a fixed triangular bracket. When the bracket is positioned so that the grippers engage the front and back of a stud, any downward force on the horizontal arm serves to increase the force exerted by the grippers on the stud. Scaffold planking can then be placed across the horizontal arms of two or more brackets.
In all of the above described prior art devices, the supporting triangular brackets, no matter how mounted, were individual units which had to be used in combination with at least one other of the same kind to provide separated positions from which to suspend scaffolding. Further, the lateral stability of each bracket depended on the stability of the member to which it was mounted, typically a stud of some type. If the stud twisted, the brackets would rotate. Conversely, the extended support arms of the triangular brackets provide a long moment arm with which to twist the vertical supports (studs) if caution is not exercised and a torque is inadvertently applied. Finally, in building construction, access to the rear side of a stud as is required for many of the bracket mounting schemes is not possible once exterior sheathing has been applied. These, and other problems with the prior art devices are eliminated or solved with the brace of this invention.